1. Field of the Invention
The present invention relates a heat-assisted magnetic recording medium and a magnetic storage device.
2. Discussion of the Background
Heat-assisted recording, in which a medium is irradiated with near-field light or the like to locally heat the surface and the magnetic coercive force of the medium is thereby reduced to write on the medium, is attracting attention as a next-generation recording mode which can achieve a surface recording density in the order of 1 Tbit/inch2. As heat-resist recording media, those employing an FePt alloy having an L10 type crystal structure in a magnetic layer are used. The above-mentioned FePt alloy has a high magnetocrystalline anisotropy Ku in the order of 106 J/m3, and therefore the magnetic particle size can be reduced to about 6 nm or less while maintaining heat stability. Medium noises can be thereby reduced while maintaining heat stability.
For obtaining a heat-assisted recording medium having a high perpendicular magnetic anisotropy, the L10 type FePt alloy used in a magnetic layer should have a good (001) orientation. For achieving this, an appropriate material should be used in a foundation layer. For example, Japanese Patent Laid-Open Publication No. 11-353648 discloses that an FePt magnetic layer shows a (001) orientation by using an MgO foundation layer. MgO has an NaCl structure, with its lattice constant being 0.421 nm, which is close to the a axial length of an FePt alloy having an L10 structure. Therefore, by forming an FePt magnetic layer on an MgO foundation layer which is (100)-oriented, the magnetic layer can be made to have a (001) orientation. Furthermore, J. Vac. Sci. Technol. B 25 (6), 1892-1895 (2007) discloses that an FePt magnetic layer shows a (001) orientation by using a TiN foundation layer. Like MgO, TiN has an NaCl structure and its lattice constant is close to that of MgO. Therefore, as in the case of MgO, the FePt magnetic layer can be made to have a (001) orientation.